is the medium for exchange of nutrients and wastes for the body's cells.

is regulated to remain relatively constant by the specialized activities of many of the body's cells.

is the extracellular fluid compartment of the body.

All of the above are correct.

by the balance of sympathetic and parasympathetic activity to them.

primarily by the mean arterial blood pressure.

solely by the activity of the sympathetic nerves innervating them.

by the balance between local factors acting on them and the activity of the sympathetic nerves innervating them.

Lipid soluble substances diffuse through the endothelial cells of the capillary wall down their concentration gradients.

Their walls do not contain any smooth muscle.

Non-lipid soluble substances are moved across the capillary wall by active transport.

The velocity of blood flow is slowest in the capillaries.

It involves the entry of a small amount of calcium through L-type calcium channels, which triggers the release a larger amount of calcium from the sarcoplasmic reticulum

Calcium released from the sarcoplasmic reticulum functions in cardiac excitation-contraction coupling by combining with troponin

The SERCA pump removes calcium from the cytosol

The amount of calcium released from the sarcoplasmic reticulum usually saturates all troponin binding sites

maintaining a stable external environment.

maintaining a stable internal environment.

both the unwavering control of a physiological setpoint and maintaining a stable internal environment are correct.

the unwavering control of a physiological setpoint.

Slow conduction of action potentials along the cell membranes of atrial muscle

Slow velocity of conduction of action potentials in the atrioventricular node

Slow conduction of action potentials by the network of Purkinje fibres in the ventricles

The shallow slope of the pacemaker potentials of the atrioventricular node

generally only fire action potentials when they are stimulated by sympathetic nerves.

have the fastest natural rhythm of all the pacemaker cells in the heart.

are a type of nerve cell specialized for rapid conduction of action potentials.

are the only pacemaker cells in the heart.

there is an increase in activity in the sympathetic nerves which innervate the arterioles.

the capillaries within the organ dilate.

cardiac output has been increased in anticipation of the increased metabolic demand.

the smooth muscle of the arterioles relaxes in response to local chemical factors.

flows against a much higher total resistance than blood in the pulmonary circulation.

flows from the left ventricle back to the left atrium.

supplies all of the organs and tissues in the body except the lungs and brain.

is equal in volume to the blood within the pulmonary circulation.

has the fastest natural rate of spontaneous action potential generation.

lies in the right atrium.

receives both sympathetic and parasympathetic innervation.

provides the only electrical connection between the atria and the ventricles.